1. Field of the Invention
The present invention relates to the linking of legacy signals to wideband networks and more particularly to an adapter/coupler, which utilizes low latency techniques and the inherent features of selected industry open standard network protocols.
2. Description of the Related Art
Modem electronics and avionics systems rely on a variety of signal interconnection techniques and methods to communicate necessary information between elements of the system. These techniques and methods rely on information protocols and physical layer transmission media suitable to the transmission of the necessary information and have often evolved into and been documented as industry communications standards.
The earliest and simplest methods were of low bandwidth point-to-point and multi-drop type connections such as single-ended and differential discretes, serial data protocols such as RS-232/422/485, which commonly work up to approximately 112 Kbps, and in some synchronous versions up to 1-10 Mbps, as well as moderate speed bus-based multiple node networks such as MIL-STD-1553, which operates at a speed of 1 Mbps. Many of these, in their original form, were developed as long as 30-40 years ago. These formats and methods are termed here as xe2x80x9clegacyxe2x80x9d signals.
More recent buses, developed within the last decade, include ones such as the IEEE-1394 standard (Firewire) and Fibre channel. These latter buses operate at speeds about two or three order of magnitude higher (currently 400 to 800 Mbps, or higher) than the legacy signals, and are accordingly classified as wideband networks.
The proliferation of interconnection methodologies accumulated over the years, and the tendency of manufactures of electronics products to design to the more common earlier legacy signal standards, has led to a situation where many different connection and bus types are simultaneously present in modern complex electronics systems. Each of these legacy signal types typically require their own set of dedicated wiring between sources and destinations, some extending considerable lengths throughout a vehicle system, adding weight and cost to finished system products.
Prior art describes the use of remote terminals to interface legacy signal types to higher bandwidth master buses. Such techniques rely on storing incoming and outgoing data from the remote terminal in buffers for transmission at convenient intervals, thereby introducing significant time latency to signals passed. These latencies require the remote terminal to first satisfy all of the signal passing handshaking required by an originating legacy signal. The data is then passed over the wideband network bus, and a new legacy signal message is created at the destination with a separate handshake transaction to complete the transfer. This process essentially breaks each message into two separately negotiated message components, each with potentially significant delays. Such delays can be critical for control systems which depend on low data latencies for stable feedback loop closures.
It is therefore a principal object of the present invention to provide a single network type for transporting data from all nodes in a system, including interfacing with legacy signal types.
It is another object to accomplish such data transportation with low latency to support the objectives of high bandwidth control systems loop closures.
It is another object to transfer timing information between network nodes with a low degree of data latency variability, i.e., jitter.
It is yet another object to accomplish the above while minimizing power consumption to implement the wideband network.
It is a further object to lower the overall total weight and cost of system signal interconnects in complex modern avionics and electrical systems.
These and other objects are accomplished by the adapter/coupler of the present invention, which links at least one legacy signal to a wideband network having a defined protocol. The adapter/coupler may be used with a wideband network having a signaling speed of 90 megabits per second, or greater. The adapter/coupler includes a signal conversion/conditioning element for receiving at least one legacy signal and providing a conditioned digital signal which is compatible to the defined protocol of the wideband network. A low latency controller element receives the conditioned digital signal and provides data/control signals. A link/physical layer element receives the data/control signals and transforms them to appropriate signaling mechanisms of a defined physical layer standard in accordance with the defined protocol. The transformed signals are outputted to the wideband network. The latency from the reception of the conditioned digital signal from the signal conversion/conditioning element to the output of the transformed signals to the wideband network is less than 200 microseconds. The adapter/coupler of the present invention introduces a wide bandwidth transmission capability to accommodate the needs of present day and future systems.
In a preferred embodiment the present invention utilizes the IEEE 1394.a standard. This provides the lowest operating power in the wideband network class and the most efficient protocol for accommodating simultaneous asynchronous and isochronous data transmission.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.